Diverse problems can arise in an electronic chip comprising field-effect transistors.
In particular, one problem in such transistors is that, in general, the smaller the transistors, the higher, in relative value, the leakage current. This results in high energy consumption.
Another problem is that, when several transistors are designed to be identical, these transistors in fact generally exhibit different electrical characteristics, in particular different threshold voltages. The differences between these electrical characteristics usually tend to get worse when the operating temperature decreases. This results in diverse difficulties in actually obtaining the envisaged electrical characteristics. These difficulties arise particularly in the case where the chip is provided for analogue operation, for example, in a measurement device, and/or for cold operation, for example, at negative ambient temperature. This usually leads to certain chips being rejected during post-fabrication checking.
Moreover, an electronic chip can comprise memory points of floating gate transistor type, surmounted by a control gate. In addition to the above-mentioned problems in respect of the transistors, such memory points exhibit problems of degradation of the transistor's gate insulator due to the fact that relatively high voltages are required to be applied for the programming of the memory points.
The diverse known methods for solving the diverse problems mentioned hereinabove require numerous fabrication steps if it is desired to implement them simultaneously for different types, N-channel and P-channel, of transistors and/or of memory points.